Torsion bar draft load adjuster

ABSTRACT

A draft load sensing mechanism for a vehicle having a torsion bar with means for presetting the minimum draft load and load range sensed by the draft load sensing mechanism.

United States Patent 1191 Peterson [541 TORSION BAR DRAFT LOAD ADJUSTER[75] Inventor: Donald E. Peterson, Milwaukee,

Wis.

[73] Assignee: Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

22 Filed: Dec.24, 1970 21 Appl. 110.; 101,323

[ [51] Int. Cl. .;.....A0lb 63/112 [58] Field of Search ..172/2, 8, 10,239, 7

1 51 Mar. 27, 1973 [56] References Cited UNITED STATES PATENTS 3,246,7024/1966 Carlin ..l72/l0 3,239,013 3/1966 Hanssmann 172/10 3,022,8312/1962 Hess .l72/7 Prim'ary Examiner-William B. Penn AssistantExaminer-R. T. Rader Att0rneyArthur L. Nelson, Kenneth C. McKivett andRobert B. Benson [57] ABSTRACT A draft load sensing mechanism for avehicle having a torsion bar with means for presetting the minimum draftload and load range sensed by the draft load sensing mechanism.

6 Claims, 3 Drawing Figures PATENTEDHARZHEIB 22,553

'SHEET 1!]? 2 TORSION BAR DRAFT LOAD ADJUSTER This invention relates toa draft responsive control system for a tractor and more particularly toa torsion bar load sensing device having a preload stop with means toadjust the minimum torque load on the torsion bar and the maximum torqueload on the torsion bar which will generate a draft load sensing signal.

A tractor having a weight distribution system is provided with a draftsensing mechanism to initiate a signal in response to a draft load. Thesignal is transmitted through a linkage to operate a valve in ahydraulic system to either raise the implement in response to anincrease in load or lower the implement in response to a decrease in theload sensed. The draft sensing mechanism is provided between the draftarms and the vehicle to sense the draft load and initiate a signal inresponse to draft load which controls the valve in the hydraulic systemfor weight distribution of the tractor and implement to thereby providethe proper traction required for the particular load applied to thedraft mechanism of the tractor.

The use of a torsion member as the draft sensing member interconnectedbetween the draft arms and the tractor resists forces applied to thedraft arms. Such mechanisms are usually preloaded by placing a torque onthe torsion bar thereby preventing operation of the sensing means underlight draft loads and are also provided with a stop to prevent overstress of the torsion bar when it is subjected to excessive draft loads.

A typical example of the prior art is disclosed in the U.S. Pat. toCarlin No. 3,246,702 which discloses a preloading means consisting of athreaded screw contacting an abuting surface on an arm'and a maximumload limit stop which is fixed and limits the maximum torque applied tothe torsion bar. It can be seen from the Carlin reference that thepreload adjustment also reduces the sensing range or the distancebetween the stop member and the abuting surface on the arm. In otherwords, when the preload stress on the torsion bar is increased the rangeof torsional movement of the torsion bar is decreased. This coupled withthe fact that the stop member is a casting and subject to relativelywide manufacturing tolerances meant that the sensing range or thedistance between the preload position and the maximum stop wasinaccurately controlled.

The present invention contemplated an advance in the art by providing animproved preload and stop means in which the adjusting screw serves thedual function of providing the preload adjustment and also acts as amaximum load stop. An important feature of this improved device is thatthe preload adjustment has no effect on the load sensing range. Afurther feature of the invention is that both abuting surfaces for thepre load and maximum stop are in a single casting and formed by a singlecore thereby minimizing manufacturing variations and permittingrelatively accurate control of the sensing range.

It is an object of this invention to provide a draft load sensingmechanism having means for setting the preload torque on the torsion barand the draft load range of the torsion bar.

It is another object of this invention to provide a draft load sensingmechanism including a torsion bar having an adjustable preload and draftload limit stop mechanism for maintaining the range of draft loadsensitivity.

It is a further object of this invention to provide a load sensitivemechanism including a torsion bar having a draft load eccentricallyapplied to the torsion bar with means adjustable preloading minimumdraft load for initiating a draft signal and providing a limit stopwhich determines the maximum draft load providing a draft signal fromthe draft load sensing mechanism.

The objects of this invention are accomplished by providing a torsionbar which is spline connected to the vehicle chassis and received withina torsion tube which forms a spline mating a spline on the opposite endof the torsion bar. A pair of ears on each end of the torsion tubeconnects to the lower draft arms which carry the draft load of thevehicle when a load is applied to the draft arm. The torsion bar carriesthe draft load and the torque applied to the torsion bar causes a stressin the torsion bar in response to the draft load which initiates asignal transmitted through a linkage from the draft sensing mechanism tocontrol a valve in the hydraulic weight distribution system. The torsiontube also carries a flange having a threaded opening to receive a boltto provide adjustable movement within the threaded opening. The chassisdefines a preload abutment and a limit stop in spaced relation to eachother on opposite sides of the adjustment screw carried in the flange ofthe torsion tube. The adjustment screw also carries a lock nut whichlocks the adjusting screw in a preset position whereby the screw endengages a preload abutment to provide a predetermined torque in thetorsion bar which determines the minimum load at which the draft loadwill initiate a signal. The head of the bolt engages a limit stop whichdetermines the maximum load which will generate a signal in response toan increasing draft load on the draft arms. Accordingly, the end of thescrew is adjustably positioned to preset the minimum draft load whilethe length of the screw determines the load range through which a draftsignal is generated. The screw may be of any predetermined length toaccomodate the draft range desired.

The preferred embodiments of this invention are illustrated in theattached drawings.

FIG. 1 illustrates the side elevation view of the tractor hitch andimplement;

FIG. 2 is an enlarged side elevation view of the draft sensing mechanismwith the draft load adjuster;

' FIG. 3 is a cross section view taken on line III-III of FIG. 2.

Referring to the drawings the tractor 1 includes a wheel 2 and one ofthe rear axles 3 in the axle housing 4. The rear drive housing 5provides a support for the bracket 6 supporting the upper link 7. Therock shaft 8 is operated by a hydraulic actuator in response to ahydraulic valve controlled by the linkage 9. The rock shaft 8 pivots therock arm 10 to raise the lift links 11 which are positioned on each sideof the tractor and connected to draft arms 12 and 13. The upper link 7is connected to the mast 14 on the implement 15. The lower draft arms 12and 13 are connected to the lower end of the mast 14.

The rear drive housing 5 supports the left hand rear axle housing 4 andthe right hand rear axle housing 17. The left rear axle housing 4 formsa cylindrical opening 18 and the right hand rear axle housing 17 definesa cylindrical opening 19 which journal the torsion tube 20. Torsion tube20 forms a spline 21 on its internal right hand end which receives themating spline 22 on the torsion bar 23. The torsion bar 23 extends intoa Spline 24 in a left hand rear axle housing 4 which is con nected tothe spline 25 on the left hand end of the torsion bar 23. Accordinglythe torsion tube 23 is locked in the left hand rear axle housing 4 andalso the right hand end of the torsion bar is locked within the splineon the right hand end of the torsion tube 20.

The ears 26 and 27 are welded to the torsion tube 20 on the right handend while the ears 28 and 29 are welded to the external periphery of thetorsion tube 20 on the left hand side. A pin 30 is received withinopenings in the ears 26 and 27 while a pin 31 is received withinopenings on the cars 28 and 29. Pin 30 is embraced by the ball sleeve 32carrying the draft arm 13 while pin 31 is embraced by the ball sleeve 33which carries the left hand draft arm 12. The draft load applied to thedraft arms 12 and 13 causes the torsion tube to rotate and produce atorque on the torsion bar 23 since the torsion bar is not free to rotatewithin the housing 4.

Lever 34 is also welded to the torsion tube 20 and is pivotallyconnected to the link 35 of the linkage 9 which operates the hydraulicvalve in the hydraulic weight distribution system. It can be seen that adraft load on the draft arms 12 and 13 will create a stress in thetorsion bar 23 which in turn will produce a displacement signaltransmitted through the lever 34 to the linkage 9.

The flange 37 is integral with the torsion tube 20. The protrusion 38forms a threaded opening 39 which threadedly receives the bolt 40. Thebolt 40 is locked on the end of the protrusion 38 by the lock nut 41.The end 42 of the bolt 40 engages a surface 43 on the preload abutment44. The surface 45 on the left hand rear axle housing 4 forms a limitstop 46. Accordingly as the torsion tube 20 rotates the bolt operatesbetween the preload abutment 44 and the limit stop 46 which determinesthe range of rotational movement responsive to the draft load applied tothe draft arms 12 and 13.

The operation of this device will be described in the followingparagraphs.

During normal operation it is desirable to prevent operation of thesensing mechanism under light draft load conditions and to also activelyprevent overstress of the torsion bar when subjected to excessive draftloads. Accordingly, a preload is applied to the torsion bar 23 byapplying a torque to the bar which in turn causes a prestress in thebar. This is accomplished through the cap screw 40 which is tightenedagainst the surface 43 of the preload abutment 44. As the cap screw 40is advanced in the threaded opening 39 the flange 37 carried on thetorsion tube produces a stress in the torsion bar 23. This eliminatesany looseness or play of the torsion bar and presets the minimum draftwhen no draft load is applied to the draft arms 12 and 13. The limitstop 46 defines the surface 45 which engages the head 50 of the capscrew 40. As the head 50 of the cap screw 40 engages the surface 45 thetorsion tube 20 is prevented from further rotation about its journaledposition in the drive shaft housing. Accordingly any further draft loadapplied to the draft arms 12 and 13 is ineffective in generating anyincrease in the displacement signal transmitted through the linkage 9.

it is understood that the distance between the abuting surfaces 43 and45 is accurately held and is formed on a single member to produce anopening of a predetermined dimension. The length of the cap screw isproduced to an exact length and so accurately controls the sensing rangeof the distance between the head and the abuting surface 42 of the capscrew. If a greater or lesser range is desired a different length of thecap screw may be used to provide the range desired.

It should also be noted that the magnitude of preload has no effect onthe sensing range of the torsion bar and the total linkage travel isused for precise positioning of the hydraulic control throughout thedraft load range for most effective weight transfer. The preload andmaximum load limit stop for the torsion bar is provided on both ends ofthe bar thereby assuring positive control and effectively eliminatingthe possibility of failure due to unequal draft loading in the lowerdraft links.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A draft load sensing mechanism for a vehicle comprising a vehiclechassis, a torsion bar connected to said vehicle chassis, a pair ofdraft arms, draft load transmitting means including a torsion tube withears extending downwardly for connecting said draft arms to said torsionbar to apply a torque to said torsion bar in response to the draft loadon said draft arms, a fixed preload abutment on said chassis, a fixedmaximum load limit stop on said chassis disposed at a predetermineddimension from said abutment, a preload torque adjusting means connectedto said torsion tube including a screw member of a predetermined shorterdimension than the dimension between said abutment and said stop alignedbetween said abutment and said stop to define a fixed operating range ofsaid sensing mechanism, said screw member adjustably positioning saidpreload torque adjusting means to adjustably set the preload torque onsaid torsion bar while maintaining a constant operating load range forproducing a displacement signal from said torsion bar in response to thedraft load applied to said draft arms.

2. A draft load sensing mechanism for a vehicle as set forth in claim 1wherein said torsion tube receives said torsion bar, said preloadabutment and load limit stop defined by said chassis positioned inangular spaced relation to each other, said screw member of said preloadtorque adjusting means connected to said torsion tube being angularlypositioned intermediate said abutment and said limit stop, said screwmember of said torque load adjusting means thereby engaging said preloadabutment to provide a predetermined torsional stress in said torsion barand for engaging said limit stop to limit the operating load range forsaid draft load sensing mechanism.

3. A draft load sensing mechanism as set forth in claim 1 wherein saidtorque adjusting means includes said screw member and a locknut lockingsaid screw member in any adjusted position.

4. A draft load sensing mechanism for a vehicle as set forth in claim 1wherein said preload torque adjusting means defines a threaded openingin said screw member threadedly engaging said opening in said preloadtorque adjusting means to thereby provide adjustable means forpresetting the preload torque on said torsion bar by engaging saidpreload abutment and limiting the maximum signal from said load sensingmechanism by engaging said limit stop.

5. A draft load sensing mechanism for a vehicle as set

1. A draft load sensing mechanism for a vehicle comprising a vehiclechassis, a torsion bar connected to said vehicle chassis, a pair ofdraft arms, draft load transmitting means including a torsion tube withears extending downwardly for connecting said draft arms to said torsionbar to apply a torque to said torsion bar in response to the draft loadon said draft arms, a fixed preload abutment on said chassis, a fixedmaximum load limit stop on said chassis disposed at a predetermineddimension from said abutment, a preload torque adjusting means connectedto said torsion tube including a screw member of a predetermined shorterdimension than the dimension between said abutment and said stop alignedbetween said abutment and said stop to define a fixed operating range ofsaid sensing mechanism, said screw member adjustably positioning saidpreload torque adjusting means to adjustably set the preload torque onsaid torsion bar while maintaining a constant operating load range forproducing a displacement signal from said torsion bar in response to thedraft load applied to said draft arms.
 2. A draft load sensing mechanismfor a vehicle as set forth in claim 1 wherein said torsion tube receivessaid torsion bar, said preload abutment and load limit stop defined bysaid chassis positioned in angular spaced relation to each other, saidscrew member of said preload torque adjusting means connected to saidtorsion tube being angularly positioned intermediate said abutment andsaid limit stop, said screw member of said torque load adjusting meansthereby engaging said preload abutment to provide a predeterminedtorsional stress in said torsion bar and for engaging said limit stop tolimit the operating load range for said draft load sensing mechanism. 3.A draft load sensing mechanism as set forth in claim 1 wherein saidtorque adjusting means includes said screw member and a locknut lockingsaid screw member in any adjusted position.
 4. A draft load sensingmechanism for a vehicle as set forth in claim 1 wherein said preloadtorque adjusting means defines a threaded opening in said screw memberthreadedly engaging said opening in said preload torque adjusting meansto thereby provide adjustable means for presetting the preload torque onsaid torsion bar by engaging said preload abutment and limiting themaximum signal from said load sensing mechanism by engaging said limitstop.
 5. A draft load sensing mechanism for a vehicle as set forth inclaim 1 wherein said torsion tube defines an internal spline, saidtorsion bar defines a mating spline for reception in said spline of saidtube, said torsion tube thereby applying a torsional stress to saidtorsion bar in response to draft load.
 6. A draft load sensing mechanismfor a vehicle as set forth in claim 1 wherein said torsion tube includesa lever integral with said torsion tube adapted for transmitting asignal to a hydraulic weigh distribution system.